水稻资源芽期和苗期耐盐碱性综合评价及耐盐基因分析

培育耐盐碱水稻品种是应对全球人口日益增长的重要途径之一。文中以21份耐盐碱性不同的水稻品种(系)为材料,在芽期和苗期设置6个不同盐碱浓度处理,测定了发芽势、发芽率、芽长、根长、根数、芽鲜重和苗鲜总重等指标,以各指标盐害率的平均值作为耐盐碱性的综合评价标准。结果表明随着盐碱浓度的提升,对种子萌发和生长的抑制越明显。在1%NaCl加0.25%NaHCO3溶液处理下,发芽率盐害率变异最大,为0%–89.80%。在所有浓度处理下,各性状指标的盐害率都具有相似的变化趋势。筛选到4份综合耐盐碱能力强(大酒谷、日本晴、魔王谷和02428)和7份弱的种质资源。比较了4份耐盐碱强和3份耐盐碱弱的资源耐盐基因序列:OsHAL3和OsRR22基因在7份材料中没有差异,SKC1和DST基因在耐盐碱强和耐盐碱弱的品种之间有明显的变异。研究结果为进一步挖掘水稻耐盐碱基因和培育耐盐碱水稻新品种提供了种质资源和理论基础。     

Induction of aluminum tolerance in wheat seedlings by low doses of aluminum in the nutrient solution

Preincubation of wheat (Triticum aestivum L. Thell.) seedlings in a nutrient solution containing low doses of aluminum (0.5 microgram per milliliter for tolerant cultivar Atlas 66 and 0.1 microgram per milliliter for the sensitive cultivar Grana) enabled substantial root regrowth of varieties grown in a lethal aluminum concentration, despite an increased accumulation of aluminum in root tissue of the pretreated seedlings. The distribution of aluminum in the subcellular fractions remained unchanged. The increase in tolerance was completely abolished by the addition of cycloheximide. Aluminum ions at sublethal concentrations significantly increased the incorporation of [¹⁴C]valine and [³H]thymidine in roots. The possible role of the synthesis of the inducible aluminum binding protein in the mechanism of aluminum tolerance is discussed.     

Differences in lead tolerance between Allium cepa plants developing from seeds and bulbs

Tolerance to lead of three of Allium cepa L. varieties grown from seeds and bulbs was compared. In all cases plants developing from bulbs were found more tolerant to lead than those developing from seeds. During 10 days of exposure to lead, the difference in the tolerance index between adventitious and seedling roots was 24% on average (7-61% depending on the plant variety and the dose of lead), which was significant. In all cases, the seedlings contained more lead in their tissues than the plants that had developed from bulbs. This observation may explain a difference in lead tolerance between these developmental phases of Allium cepa.     

氮肥处理对氮素高效吸收水稻根系性状及氮肥利用率的影响

2011—2012年在土培条件下,以氮素吸收效率差异较大的15个常规籼稻为供试材料,研究氮肥运筹对不同氮效率品种根系性状、成熟期吸氮量及氮肥利用率的影响,分析影响氮高效水稻氮素吸收的主要根系性状。结果表明:(1)各氮肥处理下,成熟期吸氮量均表现为氮高效品种氮中效品种氮低效品种。适量增施氮肥及基肥+促花肥处理有利于氮高效品种吸氮量的增加,氮素吸收受品种、氮肥处理的显著影响。(2)在施氮量处理下,氮高效品种单株不定根数、单株根干重、单株不定根总长大或较大,单株根活力在常氮(N2)、高氮(N3)处理下有一定的优势;在施氮时期处理下,氮高效品种单株不定根数、单株不定根总长、单株根干重、单株根系总吸收面积、单株根系活跃吸收面积、抽穗期冠根比多数处理有优势;增施氮肥有利于促进氮高效品种单株不定根总长和单株根活力的提高,适量施氮有利于单株不定根数、单株根干重增加,前期施氮可促进不定根的发生和伸长,后期施氮有利于不定根的充实和根系生理性状的提高。此外,增施氮肥可提高各类品种冠根比;(3)在常氮、高氮处理下,氮高效品种氮肥利用率大于氮中效、氮低效品种。(4)提高单株不定根数、单株不定根总长、单株根活力及抽穗期冠根比有利于各类品种吸氮量的提高,增加根干重对氮高效品种吸氮量的提高也有显著的促进作用。结合相关分析与通径分析结果,抽穗期冠根比及单株不定根数、单株根活力、单株不定根总长、单株根干重是影响氮高效品种吸氮能力的主要根系性状。     

Zonal responses of sensitive vs. tolerant wheat roots during Al exposure and recovery

Aluminium (Al) irreversibly inhibits root growth in sensitive, but not in some tolerant genotypes. To better understand tolerance mechanisms, seedlings from tolerant ('Barbela 7/72' line) and sensitive ('Anahuac') Triticum aestivum L. genotypes were exposed to AlCl(3) 185 μM for: (a) 24 h followed by 48 h without Al (recovery); (b) 72 h of continuous exposure. Three root zones were analyzed (meristematic (MZ), elongation (EZ) and hairy (HZ)) for callose deposition, reserves (starch and lipids) accumulation, endodermis differentiation and tissue architecture. Putative Al-induced genotoxic or cytostatic/mytogenic effects were assessed by flow cytometry in root apices. Tolerant plants accumulated less Al, presented less root damage and a less generalized callose distribution than sensitive ones. Starch and lipid reserves remained constant in tolerant roots but drastically decreased in sensitive ones. Al induced different profiles of endodermis differentiation: differentiation was promoted in EZ and HZ, respectively, in sensitive and tolerant genotypes. No ploidy changes or clastogenicity were observed. However, differences in cell cycle blockage profiles were detected, being less severe in tolerant roots. After Al removal, only the 'Barbela 7/72' line reversed Al-induced effects to values closer to the control, mostly with respect to callose deposition and cell cycle progression. We demonstrate for the first time that: (a) cell cycle progression is differently regulated by Al-tolerant and Al-sensitive genotypes; (b) Al induces callose deposition >3 cm above root apex (in HZ); (c) callose deposition is a transient Al-induced effect in tolerant plants; and (d) in HZ, endodermis differentiation is also stimulated only in tolerant plants, probably functioning in tolerant genotypes as a protective mechanism in addition to callose.     

Constitutive and aluminium-induced patterns of phenolic compounds in two maize varieties differing in aluminium tolerance

Aluminium tolerance in maize is mainly due to more efficient Al exclusion. Nonetheless, even in tolerant varieties Al can gain access into the cells. Detoxification by binding to strong organic ligands should therefore play a role also in plants with high Al exclusion capacity. To test this hypothesis in this study the concentrations of soluble, free and bound, phenolics were analyzed in roots of two maize varieties differing in Al tolerance. Exposure for 24 h to 50 μM Al in nutrient solution strongly inhibited root elongation in the sensitive variety 16 × 36, but not in the Al-tolerant variety Cateto. Cateto accumulated about half the concentration of Al in roots than 16 × 36 (analysis performed after root desorption with citrate). Roots of Al-tolerant Cateto contained higher concentrations of caffeic acid, catechol and catechin than roots of the sensitive variety. Exposure to Al induced the accumulation of taxifolin in roots of both varieties. However, Al-tolerant Cateto accumulated about twice the concentration than Al-sensitive 16 × 36 of this pentahydroxyfavonol. The molar ratio for phenolics with catecholate groups to Al was about unity in roots of Cateto, while in those of 16 × 36 the ratio was ten times lower. Both the fact that these phenolics are strong ligands for Al and their high antioxidant and antiradical activity suggest that these compounds may provide protection against the Al fraction that is able to surpass the exclusion mechanisms operating in the tolerant maize variety.     

Physiological,morphological, and growth responses ofPlatanus occidentalis seedlings to flooding

Summary Flooding ofPlatanus occidentalis L. seedlings for up to 40 days induced several changes including early stomatal closure, greatly accelerated ethylene production by stems, formation of hypertrophied lenticels and adventitious roots on submerged portions of stems, and marked growth inhibition. Poor adaptation ofPlatanus occidentalis seedlings to soil inundation was shown in stomatal closure during the entire flooding period, inhibition of root elongation and branching, and death of roots. Some adaptation to flooding was indicated by (1) production of hypertrophied lenticels which may assist in exchange of dissolved gases in flood water and in release of toxic compounds, and (2) production of adventitious roots on stems which may increase absorption of water. These adaptations appeared to be associated with greatly stimulated ethylene production in stems of flooded plants. The greater reduction of root growth over shoot growth in flooded seedlings will result in decreased drought tolerance after the flood waters recede. The generally low tolerance to flooding of seedlings of species that are widely rated as highly flood tolerant is emphasized.     

Effect of water deficit on carbohydrate status and enzymes of carbohydrate metabolism in seedlings of wheat cultivars

The effect of water deficit on carbohydrate status and enzymes of carbohydrate metabolism (alpha and beta amylases, sucrose phosphate synthase, sucrose synthase, acid and alkaline invertases) in wheat (Triticum aestivum L.) was investigated in the seedlings of drought-sensitive (PBW 343) and drought-tolerant (C 306) cultivars. The water deficit was induced by adding 6% mannitol (water potential -0.815 Mpa) in the growth medium. The water deficit reduced starch content in the shoots of tolerant seedlings as compared to the sensitive ones, but increased sucrose content in the shoots and roots of tolerant seedlings, indicating their protective role during stress conditions. It also decreased the alpha-amylase activity in the endosperm of seedlings of both the cultivars, but increased alpha and beta amylase activities in the shoots of tolerant ones. Sucrose phosphate synthase (SPS) activity showed a significant increase at 6 days of seedling growth (DSG) in the shoots of stressed seedlings of tolerant cultivar. However, SPS activity in the roots of stressed seedlings of sensitive cultivar was very low at 4 DSG and appeared significantly only at day 6. Sucrose synthase (SS) activity was lower in the shoots and roots of stressed seedlings of tolerant cultivar than sensitive ones at early stage of seedling growth. Higher acid invertase activity in the shoots of seedlings of tolerant cultivar appeared to be a unique characteristic of this cultivar for stress tolerance. Alkaline invertase activity, although affected under water deficit conditions, but was too low as compared to acid invertase activity to cause any significant affect on sucrose hydrolysis. In conclusion, higher sucrose content with high SPS and low acid invertase and SS activities in the roots under water deficit conditions could be responsible for drought tolerance of C 306.     

Identifying aluminum tolerance in rice with a molecular marker

Improving rice aluminum (Al) tolerance in acid soils is highly significant to rice production. So far, no molecular marker which can efficiently identify rice Al tolerance has been developed. In this study, Art1, a primer specific for the ART1 gene was designed to study whether some natural variations exist in ART1 between Al tolerant and sensitive varieties. The results showed that two Al tolerant varieties had identical nucleotides and amino acids, while three Al sensitive varieties had the same nucleotides and amino acids differing from the two Al tolerant varieties. The same results were discovered within 150 rice varieties of Ting’s core collection. Art1 could be used to judge rice Al tolerance.     

Salinity tolerance of japonica and indica rice (<Emphasis Type="Italic">Oryza sativa</Emphasis> L.) at the seedling stage

In order to identify the degree of salinity tolerance of the indica and japonica rice groups, 10 varieties were tested under saline and non-saline conditions. Twelve-day-old seedlings were grown in normal culture solution, then initially salinized at an electrical conductivity (EC) of 6 dS/m for 4 days, and finally salinized at an EC of 12 dS/m for the next 14 days. The growth parameters, and Na and K absorption in the shoot were measured to characterize the tolerance level of the two rice groups. Reduction in all growth parameters of tolerant varieties was significantly lower in indica varieties than in japonica varieties. Tolerant indica varieties were good Na excluders, absorbed high amounts of K, and maintained a low Na/K ratio in the shoot. Tolerant japonica varieties also absorbed less Na but were not as good excluders as indica varieties. Shoot K concentration alone did not show any relationship to salinity tolerance. These results indicate that, for all parameters measured, the tolerance level of indica was higher than that of japonica.     

Responses of Melaleuca quinquenervia seedlings to flooding

Abstract Studies were conducted on effects of flooding for 15, 30, 60, and 90 days on morphological changes, stomatal aperture, water potential, and growth of seedlings of Melaleuca quinquenervia, a species often planted for reclamation of swamps. Flooding rapidly induced formation of many hair-like adventitious roots as well as a few thick adventitious roots that originated on the original root system. Some adventitious roots also formed on submerged portions of the stem. Melaleuca seedlings were very tolerant of flooding as shown by only slight reduction in dry weight increment of shoots after 30 days of flooding in stagnant water. Although flooding for 60 or 90 days significantly reduced dry weight increment of leaves, dry weight increment of roots was not inhibited by any flooding treatment, reflecting both degeneration of some of the original roots and compensatory growth of adventitious roots. On certain days flooding induced stomatal closure on both adaxial and abaxial leaf surfaces. Extensive production of adventitious roots and some stomatal reopening after a critical period of flooding appeared to be important factors in the flooding tolerance of Melaleuca and are consistent with its aggressiveness and vigorous growth on wet sites.     

Waterlogging tolerance in the tribe Triticeae: the adventitious roots of Critesion marinum have a relatively high porosity and a barrier to radial oxygen loss

Nine species from the tribe Triticeae – three crop, three pasture and three ‘wild’ wetland species – were evaluated for tolerance to growth in stagnant deoxygenated nutrient solution and also for traits that enhance longitudinal O₂ movement within the roots. Critesion marinum (syn. Hordeum marinum) was the only species evaluated that had a strong barrier to radial O₂ loss (ROL) in the basal regions of its adventitious roots. Barriers to ROL have previously been documented in roots of several wetland species, although not in any close relatives of dryland crop species. Moreover, the porosity in adventitious roots of C. marinum was relatively high: 14% and 25% in plants grown in aerated and stagnant solutions, respectively. The porosity of C. marinum roots in the aerated solution was 1·8–5·4‐fold greater, and in the stagnant solution 1·2–2·8‐fold greater, than in the eight other species when grown under the same conditions. These traits presumably contributed to C. marinum having a 1·4–3 times greater adventitious root length than the other species when grown in deoxygenated stagnant nutrient solution or in waterlogged soil. The length of the adventitious roots and ROL profiles of C. marinum grown in waterlogged soil were comparable to those of the extremely waterlogging‐tolerant species Echinochloa crus‐galli L. (P. Beauv.). The superior tolerance of C. marinum, as compared to Hordeum vulgare (the closest cultivated relative), was confirmed in pots of soil waterlogged for 21 d; H. vulgare suffered severe reductions in shoot and adventitious root dry mass (81% and 67%, respectively), whereas C. marinum shoot mass was only reduced by 38% and adventitious root mass was not affected.     

Phosphorus deficiency enhances aluminum tolerance of rice (Oryza sativa) by changing the physicochemical characteristics of root plasma membranes and cell walls

The negative charge at the root surface is mainly derived from the phosphate group of phospholipids in plasma membranes (PMs) and the carboxyl group of pectins in cell walls, which are usually neutralized by calcium (Ca) ions contributing to maintain the root integrity. The major toxic effect of aluminum (Al) in plants is the inhibition of root elongation due to Al binding tightly to these negative sites in exchange for Ca. Because phospholipid and pectin concentrations decrease in roots of some plant species under phosphorus (P)-limiting conditions, we hypothesized that rice (Oryza sativa L.) seedlings grown under P-limiting conditions would demonstrate enhanced Al tolerance because of their fewer sites on their roots. For pretreatment, rice seedlings were grown in a culture solution with (+P) or without (−P) P. Thereafter, the seedlings were transferred to a solution with or without Al, and the lipid, pectin, hemicellulose, and mineral concentrations as well as Al tolerance were then determined. Furthermore, the low-Ca tolerance of P-pretreated seedlings was investigated under different pH conditions. The concentrations of phospholipids and pectins in the roots of rice receiving −P pretreatment were lower than those receiving +P pretreatment. As expected, seedlings receiving the −P pretreatment showed enhanced Al tolerance, accompanied by the decrease in Al accumulation in their roots and shoots. This low P-induced enhanced Al tolerance was not explained by enhanced antioxidant activities or organic acid secretion from roots but by the decrease in phospholipid and pectin concentrations in the roots. In addition, low-Ca tolerance of the roots was enhanced by the −P pretreatment under low pH conditions. This low P-induced enhancement of low-Ca tolerance may be related to the lower Ca requirement to maintain PM and cell wall structures in roots of rice with fewer phospholipids and pectins.     

Single-cell measurements of the contributions of cytosolic Na(+) and K(+) to salt tolerance

Ion concentrations in the roots of two barley (Hordeum vulgare) varieties that differed in NaCl tolerance were compared after exposure to NaCl. Triple-barreled H(+)-, K(+)-, and Na(+)-selective microelectrodes were used to measure cytosolic activities of the three ions after 5 and 8 d of NaCl stress. In both varieties of barley, it was only possible to record successfully from root cortical cells because the epidermal cells appeared to be damaged. The data show that from the 1st d of full NaCl stress, there were differences in the way in which the two varieties responded. At 5 d, the tolerant variety maintained a 10-fold lower cytosolic Na(+) than the more sensitive variety, although by 8 d the two varieties were not significantly different. At this time, the more tolerant variety was better at maintaining root cytosolic K(+) in the high-NaCl background than was the more sensitive variety. In contrast to earlier work on K(+)-starved barley (Walker et al., 1996), there was no acidification of the cytosol associated with the decreased cytosolic K(+) activity during NaCl stress. These single-cell measurements of cytosolic and vacuolar ion activities allow calculation of thermodynamic gradients that can be used to reveal (or predict) the type of active transporters at both the plasma membrane and tonoplast.     

Contribution of constitutive characteristics of lipids and phenolics in roots of tree species in Myrtales to aluminum tolerance

High aluminum (Al) concentration in soil solution is the most important factor restricting plant growth in acidic soils. However, various plant species naturally grow in such soils. Generally, they are highly tolerant to Al, but organic acid exudation, the most common Al tolerance mechanism, cannot explain their tolerance. Lower phospholipid and higher sterol proportions in root plasma membrane enhance Al tolerance. Other cellular components, such as cell walls and phenolics, may also be involved in Al tolerance mechanisms. In this study, the relationships between these cellular components and the Al tolerance mechanisms in Melastoma malabathricum and Melaleuca cajuputi, both highly Al‐tolerant species growing in strongly acidic soils, were investigated. Both species contained lower proportions of phospholipids and higher proportions of sterols in roots, respectively. Concentrations of phenolics in roots of both species were higher than that of rice; their phenolics could form chelates with Al. In these species, phenolic concentrations and composition were the same irrespective of the presence or absence of Al in the medium, suggesting that a higher concentration of phenolics is not a physiological response to Al but a constitutive characteristic. These characteristics of cellular components in roots may be cooperatively involved in their high Al tolerance.     

淹水对玉米不定根形态结构和ATP酶活性的影响

淹水２天后,玉米苗基节内即有不定根原基一进于正常植株。淹水１６天后,从基节部长出的不定根数多于正常植株,但淹水导致根系生长和干物质积累大幅度下降。淹水幼苗不定根伸长区内有发达的通气组织形成,使根内部组织孔隙度大幅提高。电镜细胞化学研究表明,经１５天淹一,不定根根尖细胞内ＡＴＰ酶的分布与正常功苗基本相同,酶活性尽管有一定的下降,但仍保持较高水平。根据实验结果,本文重点讨论了不定根的发生及其内部通气组     

Arbuscular mycorrhizal colonization and nodulation improve flooding tolerance in <Emphasis Type="Italic">Pterocarpus officinalis</Emphasis> Jacq. seedlings

Pterocarpus officinalis (Jacq.) seedlings inoculated with the arbuscular mycorrhizal fungus, Glomus intraradices, and the strain of Bradyrhizobium sp. (UAG 11A) were grown under stem-flooded or nonflooded conditions for 13 weeks after 4 weeks of nonflooded pretreatment under greenhouse conditions. Flooding of P. officinalis seedlings induced several morphological and physiological adaptive mechanisms, including formation of hypertrophied lenticels and aerenchyma tissue and production of adventitious roots on submerged portions of the stem. Flooding also resulted in an increase in collar diameter and leaf, stem, root, and total dry weights, regardless of inoculation. Under flooding, arbuscular mycorrhizas were well developed on root systems and adventitious roots compared with inoculated root systems under nonflooding condition. Arbuscular mycorrhizas made noteworthy contributions to the flood tolerance of P. officinalis seedlings by improving plant growth and P acquisition in leaves. We report in this study the novel occurrence of nodules connected vascularly to the stem and nodule and arbuscular mycorrhizas on adventitious roots of P. officinalis seedlings. Root nodules appeared more efficient fixing N₂ than stem nodules were. Beneficial effect of nodulation in terms of total dry weight and N acquisition in leaves was particularly noted in seedlings growing under flooding conditions. There was no additive effect of arbuscular mycorrhizas and nodulation on plant growth and nutrition in either flooding treatment. The results suggest that the development of adventitious roots, aerenchyma tissue, and hypertrophied lenticels may play a major role in flooded tolerance of P. officinalis symbiosis by increasing oxygen diffusion to the submerged part of the stem and root zone, and therefore contribute to plant growth and nutrition.     

Comparisons of cadmium tolerance and accumulation at seedling stage in wheat varieties grown in different decades in China

Cadmium (Cd) tolerance and accumulation in wheat varieties were investigated at seedling stage under a controlled environmental condition. The 46 leading wheat varieties cultivated from the 1950s to 2000s in China were treated at the three-leaf stage with a 50 μM CdCl₂ solution for 24 days. Growth and photosynthesis parameters were measured and the Cd-tolerance index (ratio of a given parameter under Cd treatment to that of the control) was determined. Cd accumulation in shoots and roots and Cd translocation were also determined. It was found that Cd tolerance and accumulation of these wheat varieties varied over the different decades. Principal components analysis (PCA) showed that wheat varieties in 1950s and 1980s were tolerant while varieties from the last decade were sensitive to Cd stress. Wheat varieties in 1960s and 1970s were particularly tolerant to Cd stress for the parameters of shoot height, secondary root numbers, net photosynthesis and transpiration rate while the varieties in the 1990s were sensitive to Cd stress for shoot dry weight and root dry weight. Comparing each decade to the average Cd translocation ratio from the roots to the shoots for the whole period, the varieties from the 1950s and 1960s had a higher translocation ratio, while varieties in the 1970s were below that average. Varieties from the 1980s to 2000s showed an average translocation ratio. Using cluster analysis (CA), Shannongfu 63, Yangmai 1 and Yangmai 158 were the most Cd-tolerant varieties in which Cd translocation ratio were low, and Yumai 18 and Huaimai 20 were the most Cd-sensitive varieties in which Cd translocation ratio were high. The results indicating that wheat varieties from different decades were different in Cd tolerance and accumulation, and could be useful for breeding wheat for Cd stress tolerance.     

Seedling growth variation in response to sand burial in four <Emphasis Type="Italic">Artemisia</Emphasis> species from different habitats in the semi-arid dune field

We compared seedling growth of four Artemisia species dominated at different habitats to determine whether interspecific seedling growth variation of a same genus in tolerance to burial can be used to explain plant distribution in the sand dune field. Interdune lowland species, Artemisia gmelinii, stabilized dune species, A. frigida, semi-stabilized dune species, A. halodendron, and active dune species, A. wudanica were selected. Seedlings grown for 3 weeks were treated at five burial depths for three burial times in pot experiments. Species from the habitats with little burial had smaller survival rate, dry weight and stem elongation speed than those from the habitats with intensive burial when buried. Furthermore, when buried, the former tended to adjust biomass allocation between shoot and root and produce adventitious buds, while the latter tended to maintain a constant root:shoot ratio and produce adventitious roots. We conclude that (1) seedlings of species with a long evolutionary history of exposure to sand burial (from the active sand dune), show quicker stem growth when buried than do seedlings of species from the habitats with little or no sand burial; (2) seedlings of species which do not change root:shoot ratio might be more tolerant of sand burial than those do; (3) seedlings of species from the habitats with intensive sand burial is prone to produce adventitious roots and seedlings of species from the habitats with little or no sand burial tend to produce adventitious buds when buried.     

Further studies in flood tolerance of Betula papyrifera seedlings

Flooding of soil for 60 days drastically reduced height growth, cambial growth, dry weight increment, and relative growth rate of 150-day-old Betula papyrifera Marsh. seedlings. Comparisons of responses to flooding of 150-day-old and 230-day-old seedlings indicated important differences between the two age classes. Whereas the younger seedlings produced abundant adventitious roots on submerged portions of stems, the older seedlings did not. Flooding also induced much more leaf abscission in the older seedlings. Flooding generally reduced root-shoot ratios of both age classes, largely as a result of inhibition of growth and decay of root systems. However, root-shoot ratios were altered appreciably by formation of adventitious roots in the younger seedlings and by extensive leaf abscission in the older seedlings.